This invention relates to an applicator to spread a treatment agent uniformly on the surface of molten metal in a continuous casting process. It is particularly concerned to provide an applicator to spread mold flux on to the molten metal surface in a continuous slab casting process and will be more specifically described below with particular reference to such a process.
In the casting process, flux must be applied across the surface of the molten metal in the casting mold in a uniform manner regardless of the surface area of the mold. Conventionally, this operation is carried out manually. Flux powder or granules are deposited in piles on the mold cover and are pushed in to the mold by an operator using, for example, a hoe-like tool. The operator is responsible for maintaining, so far as possible, the correct flux level over the entire mold cavity surface.
In a known alternative method, the flux is spread into the mold cavity via a fixed pipe and through a spreader tip or applicator attached to the end of the pipe. This method has not proved entirely satisfactory in that it has been found difficult to deal efficiently with any localized `hot spot` and, in this respect, the entirely manual conventional system appears to be better.
It is an object of the invention to provide an improved automated process to maintain a uniform covering of treatment agent, e.g. flux, on the surface of molten metal in a mold cavity.
Accordingly, in one aspect, the invention provides an apparatus to supply treatment agent at a treatment station, which comprises an applicator to spread the agent into the treatment station, agent feed means to supply the agent to the applicator, pressurized gas feed means outletting adjacent the applicator in at least two directions and control means for the gas feed means to enable the gas feed in each said direction to be independently controlled.
The treatment agent is preferably in granulated form but may have other physical form e.g. a powder.
The applicator is preferably a frusto-triangular shaped pan in plan whose narrow end is connected to the agent feed means. The pan is preferably flat-bottomed with a series of channels defined by vanes on its upper surface so that the flow of treatment agent is divided along those channels and then exits at the wider end of the pan. Alternatively, the bottom of the pan may be, for example, corrugated or domed.
The gas feed means preferably outlet into or somewhat before the narrow end of the pan to control the distribution of the treatment agent into the various channels.
The agent feed means is preferably a stainless steel tube connected to a hopper containing the treatment agent. Conventional means may conveniently be employed to supply the hopper with treatment agent and to deliver the treatment agent from the hopper to the agent feed means and then the applicator.
In another aspect the invention provides an apparatus to supply treatment agent to a treatment station which comprises an applicator to spread the agent at the treatment station, an agent feed means comprising a tube from a source of the agent, a trough to receive the end of the tube remote from the source, the trough leading into the applicator and a wedge-shaped distributor positioned in the trough with its narrow end towards the tube and its wider end towards the applicator whereby the agent passing through the trough is spread out across its width.
The wedge-shaped distributor may, for example, be attached to the base of the trough, but in a preferred embodiment, is suspended above the base.
In another aspect the invention provides an applicator to supply treatment agent to a treatment station, the applicator being of generally frusto-triangular plan shape so as to have a narrow end and a wider end, and being adapted to be connected at its narrow end to a means of supply of the treatment agent, the surface of the applicator over which the agent is to flow comprising a series of open channels, the channels widening from the narrow end to the wider end of the applicator.
As indicated above, the applicator may be, for example, flat-bottomed, domed or corrugated. When it is of corrugated form, the corrugations may conveniently define the desired channels. When it is flat-bottomed or domed, the channels may conveniently be provided by vanes upstanding from its upper surface.
As indicated above, the treatment station will preferably be the mold cavity of a continuous slab caster and the treatment agent is preferably a flux to be applied to the molten metal surface in the mold cavity.
In a preferred embodiment there are two outlets for the pressurized gas, one at each side of the applicator pan. The gas feed may conveniently be delivered from a conventional pressurized source to pass along two tubes attached along opposite sides of the steel tube feed means for the treatment agent. A dry gas, preferably an inert gas, e.g. argon, is used as the pressurized gas.
In the preferred embodiment, therefore, the gas outlets are provided to direct the gas at the right-hand side and left-hand side of the applicator pan. The right-hand gas outlet or jet is arranged to blow the treatment agent towards the left side of the applicator and the left-hand jet is arranged to blow the treatment agent towards the right side of the applicator. The control means for the gas outlets may be manual or a programmed controller. The direction and amount of gas flow is thereby controlled to ensure the desired distribution of treatment agent across the applicator and, hence, across the mold cavity.
Thus, the invention provides a multiplicity of means to ensure the desired uniform distribution of flux.
Firstly, the wedge-shaped distributor located in the connecting trough between the tube feed means and the applicator spreads out the flux emerging from the tube more evenly across the trough and hence it is more evenly distributed as it enters the applicator.
Secondly, the applicator with its frusto-triangular or fan-shape, widening from its inlet to its outlet and with its widening channels also helps to ensure a good spread of the flux as it emerges from the applicator.
Thirdly, the gas feed means enable the distribution of the flux to be varied to meet specific needs as they arise or to be distributed according to a preferred, pre-determined pattern.
Where the wedge-shaped distributor is used in addition to the applicator and the gas feed means, it will be found advantageous to position the gas outlets to operate into the trough in the region between the distributor and the applicator.